JP2007500771A - Conductive polymer, method for producing conductive polymer, and method for controlling conductivity of polymer - Google Patents

Abstract

Disclosed is a method for controlling electrical conductivity of a polymer composition, and a polymer composition comprising a polymer resin, a conductive filler, and a dispersion control agent that promotes a substantially uniform arrangement of the conductive filler throughout the polymer composition. To do. The polymer composition is substantially free of polycyclic aromatic compounds.

Description

  The present invention relates generally to conductive polymer materials, and more particularly to polymer materials having a controllable conductivity over a concentration range of conductive fillers.

[Related applications]
This application was filed on July 29, 2003, “CONTROLLERE ELECTRICAL CONDUCTIVITY IN POLYMERS THROUGH THE USE OF CONDUCTIVE AND NON-COND. Priority is claimed based on US Provisional Patent Application No. 60 / 490,871, entitled “NANO AND MICROPARTICLES”.

  The present invention relates to a method for controlling the conductivity of a polymer material that is normally electrically insulating. More particularly, the present invention is directed to reducing the concentration of carbon black (CB) and / or other conductive particles and chemicals containing carbon nanotubes required to reach the percolation threshold of the polymer composition. , Using conductive and non-conductive nanoparticles and microparticles.

  Conventional polymer materials used to manufacture packages typically insulate the package contents from external conductive paths. Applications such as electrical and semiconductor component packages, satellite and spacecraft electromagnetic radiation shielding, and cardiac pads that form electrocardiogram electrodes need to dissipate electrostatic energy that can accumulate over time.

  Early attempts to impart electrostatic discharge (ESD) characteristics to polymer products required mixing conductive fillers such as carbon black particles with the polymer resin selected for the particular product. At the time of mixing, carbon black particles are randomly dispersed in the polymer resin. In order to disperse carbon black randomly, a moderately high carbon black concentration is required, and a moderately high carbon black concentration ensures that the conductive path extends throughout the polymer product formed from the mixed polymer resin. Is done.

  Applications that use recently developed techniques require polymer materials that have low electrical conductivity and accurate electrical conductivity within a narrow intermediate region. However, the conductivity of the polymer material in such an intermediate region of conductivity changes rapidly depending on the carbon black concentration, making it difficult to accurately control the conductivity.

  As the minimum size of electronic devices continues to decrease, the requirements for polymeric materials for packages and other applications described above become more stringent. In addition to precise control of conductivity, the permissible concentration of conductive components such as carbon black that can be released from polymer products and damage electronic devices is becoming smaller. By minimizing the carbon black concentration, the likelihood of carbon black being released from the polymer product and damaging nearby electronics is reduced.

  Polycyclic aromatic compounds have been added to the polymer resin and conductive filler composition to minimize the carbon black concentration required to establish conductivity in the polymer product. Polycyclic aromatic compounds are believed to affect the conductivity of the composition in two ways: the first is to increase the number of interparticle contacts and the second is This is a method of reducing resistance to electron transfer between conductive particles. Polycyclic aromatic compounds can affect the conductivity of the resulting polymer composite, but polycyclic aromatic compounds are often expensive and toxic and require additional protection measures during synthesis. Become. In addition, polycyclic aromatic compounds often contain metal components that can damage delicate electronic devices.

  Conventional polymer compositions known in the art include the polymer compositions disclosed in US Pat. No. 5,298,194 to Carter et al. US Pat. No. 5,298,194 discloses obtaining a conductive polymer composition by mixing polymer particles and metal particles and then applying heat and / or pressure. It is described that this composition can be used as an adhesive composition.

  Similarly, US Pat. No. 5,508,348 issued to Ruckenstein et al. Discloses a polymer composite that includes conductive polymer particles uniformly dispersed in a non-conductive polymer.

  U.S. Pat. No. 5,567,355 to Wesling et al. Discloses the formation of an essentially conductive polymer. This polymer is a dispersible solid of primary particles having a specific surface area.

  U.S. Patent No. 6,277,303, U.S. Patent No. 6,284,832, and U.S. Patent Application Publication No. 2002/0004556 all indicate conductive polymer compositions as a whole. The composition includes a main polymer phase and a subpolymer phase, and the main polymer phase and the subpolymer phase are immiscible. The secondary polymer phase includes a conductive filler. These references also disclose that the composition may include nucleating materials of talc, silica, mica, kaolin, and similar materials, but of the materials that affect the conductivity of the composition. It does not disclose the amount used, nor does it disclose any uniform mixture containing conductive fillers and non-conductive fillers.

  U.S. Patent Application Publication No. 2004/0016912 by Bandyopadhyay et al. Discloses a conductive thermoplastic composite and a method of making the same. The composite of U.S. Patent Application Publication No. 2004/0016912 includes a polymer resin, a conductive filler, and an amount of a polycyclic aromatic compound effective to increase the conductivity of the composite. Polycyclic aromatic compounds affect the conductivity of the composite by increasing the number of interparticle contacts or by reducing the resistance to electron transfer between conductive particles.

  According to one aspect of the present invention, there is provided a polymer composition comprising: a polymer resin; a conductive filler; and a dispersion control agent that promotes a substantially uniform arrangement of the conductive filler throughout the polymer composition. A polymer composition is provided that is substantially free of polycyclic aromatic compounds.

  According to another aspect of the invention, there is provided a polymer composition as compared to a polymer resin, a conductive filler, and the same composition that does not contain sub-micron to nano-sized particles. An amount of non-conductive filler effective to increase conductivity, and a polymer composition substantially free of polycyclic aromatic compounds.

  According to another aspect of the present invention, a polymer composition as compared to the percolation threshold of the same composition without polymer resin, conductive filler and non-micron to nano-sized non-conductive particles. And an amount of submicron to nano-sized non-conductive particles effective to reduce the percolation threshold of the polymer composition, the polymer composition being substantially free of polycyclic aromatic compounds. The

  According to another aspect of the invention, a polymer composition comprising a polymer resin, a conductive filler, and a sensitivity of the conductivity of the polymer composition to changes in the concentration of the conductive filler in a desired conductivity region. And a dispersion control agent in an amount effective to minimize the polymer composition, and a polymer composition substantially free of polycyclic aromatic compounds.

  According to yet another aspect of the invention, a method for controlling the electrical conductivity of a polymer composition comprising the steps of identifying a desired electrical conductivity range including a desired electrical conductivity, and an effective amount of Adding a dispersion control agent to the polymer resin, minimizing the sensitivity of the conductivity of the polymer composition within the range of the desired conductivity, adding a conductive filler to the polymer resin, and Adjusting the conductivity to the target conductivity.

  These and other features and advantages of the present invention will become apparent to those of ordinary skill in the art by reading the following description with reference to the drawings.

  Percolation theory is well known as describing the number of connections that change in a random network. For example, consider an array of holes on a substrate. When small conductive particles are randomly deposited on the substrate, the conductive particles enter the holes formed in the substrate. Since the conductive particles in the adjacent holes are arranged close enough to generate electron transfer and electric conduction, electric conduction occurs between the conductive particles arranged in the adjacent holes. . Adjacent groups of conductive particles can form clusters, which grow as metal particles are deposited on the substrate. As a result, the cluster can extend from one end of the substrate to the other, and a continuous conductive path called a spanning cluster can be formed across the substrate. Electrical conduction across the substrate does not occur until at least a minimum number of conductive particles are deposited and connect the ends of the substrate. However, the first N conductive particles required to form a spanning cluster arranged in this way are the minimum number of metal particles that are deposited before the statistical probability of the spanning cluster becomes important. More than ever.

At some point during the deposition of the conductive particles, a rapid increase in electrical conduction across the substrate occurs. The concentration of the metal particles when such an increase in electrical conduction occurs is called a percolation threshold (“V _f ^* ”), and the substrate mainly functions as an electrical insulator at a concentration lower than the percolation threshold. To do.

  The percolation theory has been described above by taking a two-dimensional substrate including an array of holes as an example, but the same principle can be applied to a three-dimensional array of holes formed on a substrate and randomly filled with metal particles. However, it is necessary that the metal particles not only be arranged across the substrate, but also be arranged so as to form a spanning cluster three-dimensionally through the substrate.

Unexpectedly, a polymer composition that is substantially free of polycyclic aromatic compounds and that includes a polymer network, a conductive filler, and an effective amount of a dispersion control agent is free of a dispersion control agent. It has been found that the percolation threshold V _f ^* is reduced compared to the same polymer composition. The dispersion control agent can be any material that promotes a substantially uniform placement of the conductive filler of the polymer composition. The almost uniform arrangement of the conductive filler in the polymer composition means that each conductive filler particle is dispersed so as to form a plurality of aggregates, and the aggregates are randomly dispersed to form a spanning cluster. Means that The dispersion control agent promotes at least one of a physical interaction and a chemical interaction between the polymer resin and the conductive filler in the combination of the polymer resin and the conductive filler. Preferred dispersion control agents include clay materials. The number of conductive filler particles required to form the spanning cluster, and thus the concentration of conductive filler, is minimized, at least in part due to the substantially uniform arrangement facilitated by the dispersion control agent.

  1a to 1c schematically show a substantially uniform arrangement of conductive fillers in the polymer composition. FIG. 1 a is a schematic diagram of random dispersion of conductive filler particles in the case where a dispersion control agent is not used, and the dispersion shown in FIG. 1 a is referred to as regular mode dispersion. Random placement of conductive filler particles in regular mode requires a much higher concentration of conductive filler than is required when using a dispersion control agent to form agglomerates. Instead of forming agglomerates that are dispersed in regular mode, each conductive filler particle is randomly dispersed within the polymer network.

  On the other hand, FIG. 1b schematically illustrates one embodiment of a substantially uniform arrangement of conductive filler particles promoted by a dispersion control agent, wherein the substantially uniform arrangement shown in FIG. 1b is agglomerated mode dispersion. Also called. As described above, each conductive filler particle forms a plurality of aggregates by the dispersion control agent, and the aggregates are dispersed in a regular mode as a whole.

  The substantially uniform arrangement or aggregation mode dispersion of the conductive filler particles can include aggregates of any size, depending at least in part on the concentration of the dispersion control agent within the polymer composition. For example, the aggregate of conductive filler particles in FIG. 1b is a larger aggregate than the small aggregate schematically shown in FIG.

  The dispersion control agent can be any material that promotes at least one of physical and chemical interactions between the polymer resin and the conductive filler in the combination of the polymer resin and the conductive filler. Preferred dispersion control agents include clay materials. Layered clay material, layered clay, layered material, clay material, and clay are interchangeable terms as a plurality of adjacent bonds. In the form of a layer, it is used to mean organic or inorganic materials or mixtures thereof (such as smectite clay minerals). Layered clay contains platelet particles and is usually expandable. By platelets and platelet particles are meant layers of clay material or agglomerated unbound layers. These layers may be in the form of individual platelet particles, regular or irregular small aggregates (tactoids) of platelet particles, and / or tactoid small aggregates.

Without being bound by theory, the dispersion control agent establishes an interaction between the conductive filler particles and the reactive sites of the polymer resin. It is believed that thermodynamic affinity between the polymer network and the dispersion control agent (herein referred to as “nanoparticles”) is necessary to allow proper dispersion / exfoliation of the nanoparticles. Such affinity can be generated in several ways. The first method is to ensure the presence of strong intermolecular forces between the polymer network and the nanoparticles. Strong intermolecular forces may be polar interactions such as nylon 6 and clay nanoparticles or other known strong bonds. In the absence of strong intermolecular forces, the polymer network can be modified to create an affinity between the polymer network and the nanoparticles. For example, when a polyolefin is modified with maleic anhydride, the polyolefin can interact with the modified clay nanoparticles. In order to increase the affinity, the interfacial chemistry of the nanoparticles can be changed to promote a strong interaction between the polymer network and the nanoparticles. Once the interaction between the polymer network and the nanoparticles is established, a partially and / or fully dispersed / exfoliated system is obtained. Mixing conductive fillers with such compositions allows for an unexpected decrease in V _f ^* and a decrease in the percolation curve slope in the desired conductivity range.

Although not impossible, it is very difficult to identify a predetermined form of interaction between the conductive filler and the polymer network in a multiphase polymer material, but the interaction is dipole-dipole interaction. It is considered to be a combination of a weak physical interaction such as an action and a strong chemical interaction such as a hydrogen bond. Regardless of the specific interaction, instead of forming a cluster at the reaction site where the first conductive filler particles were introduced, the dispersion control agent could be used for subsequently introduced conductive filler particles and polymer resin. Facilitates the formation of interactions between reactive sites. As a result, the dispersion control agent prioritizes the interaction between the conductive filler particles and the other reactive sites of the polymer resin before the cluster is formed at one reactive site of the polymer resin. In this way, the conductive filler particles are dispersed almost uniformly throughout the resulting polymer composition. The nearly uniform dispersion minimizes the concentration of conductive filler needed to form the spanning cluster, resulting in a lower percolation threshold V _f ^* .

  Further, due to the almost uniform arrangement of the conductive filler by the dispersion control agent of the present invention, the relationship between the conductivity and the concentration of the conductive filler is compared with the similar relationship of the polymer composition when the dispersion control agent is not used. And become more gradual. The curve showing the relationship between the conductivity of the polymer composition containing the dispersion control agent and the concentration of the conductive filler has a gentler slope in the desired region than the similar curve in the polymer composition not using the dispersion control agent. Have. Thus, by introducing an effective amount of a dispersion control agent into the polymer composition, the conductivity can be accurately controlled in the desired range.

The appropriate concentration of the dispersion control agent to be included in the polymer composition is determined based at least in part on the desired conductivity as well as an acceptable deviation from the desired conductivity. FIG. 2a shows a polymer composition comprising nylon 6 (“Ny6”) as a polymer resin, carbon black (“CB”) as a conductive filler, and montmorillonite (“organic clay”) as a dispersion control agent. 2 is a plot of conductive filler concentration versus conductivity. As shown in FIG. 2a, the curve of the polymer composition that does not contain a dispersion control agent (“Ny6 / CB” composition) is a stepped curve having a substantially non-inclined portion and a rapidly inclined portion. It is difficult to adjust the CB concentration of the Ny6 / CB composition to a value in the range of 10 ⁻⁷ to 10 ⁻⁶ S / cm because the slope of the Ny6 / CB curve in this range is steep. Then, the conductivity of the polymer composition becomes very sensitive to the CB concentration. A small change in the CB concentration greatly changes the electrical conductivity of the composition, making it difficult to control the electrical conductivity.

On the other hand, the curve of the polymer composition containing 3% by volume of the dispersion control agent (“Ny6 / CB / organoclay” (3% by volume) composition) has a substantially negative inverse exponential relationship with the CB concentration. The percolation threshold of the Ny6 / CB / organoclay (3% by volume) composition occurs at a CB concentration that is lower than the percolation threshold of the Ny6 / CB composition, and within a conductivity range of 10 ⁻⁷ to 10 ⁻⁶ S / cm. Has a gentler curve. It is difficult to adjust the CB concentration of the Ny6 / CB composition to a value in the range of 10 ⁻⁷ to 10 ⁻⁶ S / cm because the slope of the Ny6 / CB curve in this range is steep. Then, the conductivity of the polymer composition is affected by the CB concentration. A small change in the CB concentration causes a significant change in the conductivity of the composition, making it difficult to control the conductivity.

By including 3% by volume of organoclay in the polymer composition, the percolation threshold is reduced to about 1-3 phr CB and the conductivity is 10 ⁻⁷ to 10 ⁻⁶ S / cm at about 10 phr CB. The lower end of the range is reached and a more gentle slope of about 4.5 × 10 ⁻⁸ S / cm / phr CB is obtained. Thus, to produce a polymer composition having a desired conductivity within the conductivity range while minimizing the sensitivity of the conductivity to changes in the conductivity filler concentration and the conductivity filler concentration within the conductivity range, organic The effective amount of clay can be optimized.

  Molded articles and other products made from the polymer composition of the present invention exhibit minimal spatial variation in electrical conductivity. Products formed from conventional polymer compositions usually contain a large number of non-conductive parts, as well as other parts. Spatial variation in conductivity in conventional products is thought to be caused by random placement of conductive fillers, and instead of forming a nearly uniform network of conductive fillers, discontinuities in the polymer composition A cluster is formed at the part. On the other hand, the dispersion of the conductive filler by the dispersion control agent according to the present invention provides a polymer composition having a substantially uniform conductivity throughout. Thus, a product made from this polymer composition has substantially the same conductivity at all locations on the outermost surface, regardless of where the conductivity is measured.

  The polymer resin used for the composite material can be selected from various thermoplastic resins, thermoplastic elastomers, thermosetting resins, and one or more combinations thereof. Specific examples of suitable thermoplastic resins include, but are not limited to, polyacetal, polyacrylic acid, styrene acrylonitrile, acrylonitrile-butadiene-styrene (ABS), high impact polystyrene (HIPS), polyethylene-vinyl acetate (EVA), poly Lactic acid (for example, PLLA), polycarbonate, polystyrene, polyethylene, polyethylene oxide, polymethyl methacrylate, polyphenylene ether, polypropylene, polyethylene terephthalate, polybutylene terephthalate, nylon (for example, nylon 6, nylon 6/6, nylon 6/10, nylon 6) / 12, nylon 11, nylon 12), polyamideimide, polyarylate, polyurethane, ethylene propylene diene rubber (EPR), ethylene propylene Enmonomer (EPDM), polyarylsulfone, polyethersulfone, polyphenylene sulfide, polyvinyl chloride, polysulfone, polyetherimide, polytetrafluoroethylene, fluorinated ethylene propylene, perfluoroalkoxyethylene, polychlorotrifluoroethylene, polyfluorinated And vinylidene, polyvinyl fluoride, polyether ketone, polyether ether ketone, polyether ketone ketone, liquid crystal polymer, and a mixture containing one of the above thermoplastic resins. Preferred thermoplastic resins are polycarbonate, polybutylene terephthalate, and mixtures containing one or more of these resins.

  Specific examples of thermoplastic resin mixtures include, but are not limited to, acrylonitrile-butadiene-styrene / nylon, polycarbonate / acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene / polyvinyl chloride, polyphenylene ether / polystyrene, polyphenylene ether / nylon. , Polysulfone / acrylonitrile-butadiene-styrene, polycarbonate / thermoplastic urethane, polycarbonate / polyethylene terephthalate, polycarbonate / polybutylene terephthalate, thermoplastic elastomer alloy, nylon / elastomer, polyester / elastomer, polyethylene terephthalate / polybutylene terephthalate, acetal / elastomer, Styrene-maleic anhydride / Ac Ronitoriru - butadiene - styrene, polyether etherketone / polyethersulfone, polyether ether ketone / polyetherimide, polyethylene / nylon, polyethylene / polyacetal, polyethylene oxide / polylactic acid, polymethyl methacrylate / polyvinylidene fluoride and the like.

  Specific examples of the thermosetting resin include, but are not limited to, polyurethane, natural rubber, synthetic rubber, epoxy resin, phenol resin, polyester, polyphenylene ether, polyamide, silicone, and any one of these thermosetting resins. The mixture containing is mentioned. Mixtures of thermosetting resins and mixtures of thermosetting resins and thermoplastic resins can also be used.

  Specific examples of conductive fillers include carbon nanotubes (single wall and multiwall), vapor grown carbon fibers having a diameter of about 2.5 to about 500 nm, carbon fibers, carbon black, graphite, graphite nanoplatelets, and Carbon fillers, such as a mixture containing 1 or more types of the said filler, are mentioned.

  Specific examples of dispersion control agents include, but are not limited to, various particles having a size of at least nanometer scale. These particles include clay minerals, organically modified clay, other inorganic particles (including nanoparticles etc.) with appropriate size and shape, appropriate particle size, specific specific surface area, aggregate structure, And organic particles having surface chemistry.

  As described above, the polymer composition of the present invention further includes a conductive filler that imparts conductivity to the polymer composition. Suitable conductive fillers include solid conductive metal fillers or inorganic fillers coated with solid metal fillers. These solid conductive metal fillers may be conductive metals or alloys that do not melt under the conditions used when mixing into the polymer resin and manufacturing the finished product. A metal such as aluminum, copper, magnesium, chromium, tin, nickel, silver, iron, titanium, and a mixture containing one of these metals can be mixed with the polymer resin as solid metal particles. Physical mixtures and alloys such as stainless steel and bronze can also be used as the metal component of the conductive filler particles. Moreover, intermetallic compounds (for example, titanium diboride) such as borides and carbides of these metals can also be used as the metal component of the conductive filler particles. Solid non-metallic conductive filler particles such as tin oxide and indium tin oxide can also be added to the polymer resin. The solid metal / non-metallic conductive filler can be present in drawn wires, tubes, nanotubes, debris, laminates, platelets, ellipsoids, disks, and other commercially available forms. Carbon-based conductive particles can also be used for this purpose. Carbon-based conductive particles include chemically and physically modified carbon black, carbon nanofibers, carbon nanoplatelets, and carbon nanotubes. Metal nanoparticles can include nanotubes of metal particles and other shaped particles.

[Experiment]
In addition to the general description of the invention described above, specific embodiments are described below. This embodiment includes nylon 6 (“Ny6”) as the polymer resin, carbon black (“CB”) as the conductive filler, and montmorillonite (“organic clay”) as the dispersion control agent. In the following specific description, a conventional polymer composition containing Ny6 and CB and no dispersion control agent is described for comparison and compressed from CB-filled Ny6 and CB-filled Ny6 containing organoclay. The electrical property / CB dispersion relationship of the molded product will be described.

  CB is a known organic nanoparticle, which is formed from an aggregate of individual particles having a substantially spherical shape and a diameter on the order of nanometers. Although CB typically contains a variety of polycyclic aromatic hydrocarbons having a variety of oxidation states, the polymer composition of the present invention remains substantially free of polycyclic aromatic compounds. This means that a polycyclic aromatic compound is not substantially added other than the polycyclic aromatic hydrocarbon present on the surface of CB.

  Organoclay is a layered clay mineral inorganic compound comprising a flexible aluminosilicate platelet having a flat surface and a length of about 200 nm and a thickness of 1 nm. Organoclay has an exchangeable sodium cation between layers, is hydrophobic, and is usually not compatible with organic molecules. However, the sodium cation can be exchanged for an organic cation, improving the affinity for organic molecules.

  Polymer matrix nanocomposites with organoclay exfoliated silicate platelets have mechanical and gas barrier properties that are not readily obtainable with conventional composites. Since organoclay silicate platelets have polar groups, they have excellent affinity for polymers containing polar functional groups. This is considered to be one of the reasons that the physical properties are improved because Ny6 and the organoclay nanocomposite are compatible and the interfacial tension between Ny6 and the organoclay is small.

  Chemical modification of layered silicate platelet nanoparticles (organoclay) affects intercalation, exfoliation, and nanodispersion in polymer matrices such as nylon 6, resulting in new physical properties in nanocomposites . The organoclay within the nylon 6 matrix can be dispersed by two main methods. The first method is in situ polymerization using a mixture of ε-caprolactam and organoclay modified with 12-aminolauric acid or a long chain alkylene linked to an amino acid as a catalyst, and the positively charged amine of nylon 6 Concomitant with the end groups forming ionic bonds directly on the surface of the negatively charged silicate platelets, the interlayer distance of the organoclay is greatly increased in the presence of ε-caprolactam during polymerization. Another method is a melt blend of nylon 6 and organoclay modified with quaternary ammonium chloride (organic modifier) and / or quaternary ammonium chloride to which a hydroxyl or carboxyl group (functional group) is bonded. Nylon 6 molecular chain diffusion / penetration due to mechanical shearing increases the interlayer distance of the organoclay and forms a hydrogen bond with the functional group attached to the organic modifier at the amide group of nylon 6, or an amine The end groups have physical interactions such as London (dipole) interactions on the surface of pure silicate platelets, and the interfacial tension between nylon 6 and organoclay is very low. However, the mechanism of nylon 6-clay (or organoclay) interaction for intercalation / peeling, and the mechanism of nanoscale dispersion (or propulsion) of organoclay in the absence of shear flow are: Currently unknown.

[Material and sample preparation]
Two commercially available film grade raw material nylon 6 and a melt blend nylon 6 nanocomposite added with 3.0 vol% and 5.0 vol% organoclay (RTP, USA) were used. As conductive filler nanoparticles, commercially available low-structure rubber grade carbon black (CB) (Seast (registered trademark) G-SVH manufactured by Tokai Carbon Co., Ltd.): primary particle diameter: 62 nm, N ₂ specific surface ^area: 32m 2 / g, DBP oil ^absorption: 140cm 3 / 100g) was used.

  Raw material nylon 6, extruded pellets of nylon 6 nanocomposite and purchased pulverized CB were dried in vacuum at 80 ° C. for 24 hours prior to melt blending. Melt blending was performed using a conventional closed mixer (Plasticorder manufactured by Brabender, USA) at 245 ° C. for 10 minutes at a rotation speed of 60 rpm. A film (film thickness: 0.5 mm) and a disk (film thickness: 2.0 mm, diameter: 25 mm) are formed by compression molding at 250 ° C. for 10 minutes under a pressure of 20 MPa, and air-cooled at room temperature for 5 minutes. did.

[Conductivity measurement (ASTM D257, D4496)]
The conductivity was measured in the thickness direction of the film using a Keithley 6487 picoammeter equipped with a DC voltage source. The voltage value was about 0.001 to 5000V. The bulk conductivity of the film was determined as the average of four conductivity measurements, each conductivity measurement being obtained at a different location in the central region of the film.

[SEM observation]
The dispersion state of CB was observed with a field emission SEM (manufactured by JEOL). Samples were frozen and crushed in liquid nitrogen. The freeze fractured surface was coated with a Polaron high energy silver sputter device in a vacuum for 1 minute.

[Digital image analysis of SEM photographs]
Quantitative analysis of the CB dispersion was characterized by the least squares method (quadrate method) and statistical processing of SEM photos using the dispersion index I _[delta] of Morishita (Morishita). This index plays an important role in the characterization of the dispersion mode and is given by:

In the formula, δ is given by the following formula.
Wherein, q is the number of equally divided element parts from the total area of the SEM image (elemental parts), _{n i} is the number of particles of sections of the i, N is a total number of particles, the less It is given by the formula.

[result]
(Electrical percolation behavior)
FIG. 2a shows percolation curves for various Ny6 / CB-based compositions with different organoclay addition rates, showing a typical plot of CB concentration versus logarithmic σ at room temperature, and FIG. The logarithm (sigma) plot with respect to the volume fraction of the organoclay in CB density | concentration is shown. The formation of a conductive network does not require direct contact between the two CB particles, but requires a close enough relationship (usually on the order of nanometers) for electron tunneling to occur. The Ny6 / CB composition without organoclay showed an approximately 3 digit increase in conductivity when the CB concentration reached 30 phr (phr = weight of CB per 100 parts of resin) and was determined to be the percolation threshold V _f ^* . .

  FIG. 2a also shows the percolation curves of the Ny6 / CB / organoclay (3% by volume) composition and the Ny6 / CB / organoclay (5% by volume) composition. In each of these curves, it is clear that the percolation threshold is lower than the Ny6 / CB composition without organoclay. The percolation threshold was 10 phr CB for the Ny6 / CB / organoclay (3 vol%) composition and 20 phr CB for the Ny6 / CB / organoclay (5 vol%) composition.

  Two new percolation features were also observed. (I) When the volume percentage of the organic clay decreases, the slope of the percolation curve becomes gentler, and the slope in the percolation region (the region following the percolation threshold) is 3 (added by 5 vol%), 2.5 (3 vol%) Added), 1.5 (added by 0% by volume). Such behavior is believed to be due to the strong affinity between nylon 6 and CB. For polymer resins having no affinity for the conductive filler, the slope may increase as the clay concentration decreases. (Ii) The conductivity increased according to the volume% of the organic clay in the 30, 35, 40 phr CB which is a high CB concentration region.

  FIG. 2b shows an overview of the inventive organoclay addition induced percolation phenomenon in nylon 6-CB composites. The Ny6 / CB / organoclay (3% by volume) composition showed the highest conductivity at low CB concentration (<20 phr). At an intermediate CB concentration (20 phr <CB <40 phr), the conductivity data of the Ny6 / CB / organoclay (5% by volume) composition increases and the conductivity of the Ny6 / CB / organoclay (3% by volume) composition increases. Over. In the high CB concentration region (> 40 phr), the conductivity data of all organoclay-added nylon 6-CB systems are almost linear and stable. In each composition, low structure rubber grade CB is selected as the conductive nanoparticle, which has a dense primary aggregate, which is added when no dispersion control agent is added. It contains few primary particles that make it difficult for a particular CB to disperse to form a percolated network structure.

(Dispersion and distribution of CB and organoclay)
FIG. 3 shows typical SEM images of the Ny6 / CB 10 phr system with different organoclay addition rates. In FIG. 3, the white point of the original image (black point of the enlarged image) indicates a CB primary aggregate, and the black region of the original image (gray region of the enlarged image) indicates a nylon 6 network. In each pair of images, the left image is an original image, and the right image is an enlarged image of the same SEM image. The schematic diagram of FIG. 3d is for facilitating understanding of the SEM image. When the addition amount of the organic clay shown in FIGS. 3a and 3b is 0 to 3% by volume, the CB dispersion of the original image of FIG. 3a is “branched” and / or “chain” as shown in FIG. 3b, respectively. Has been transferred to the “morphology” morphology. This observation is consistent with the Ny6 / CB / organoclay (3% by volume) composition achieving percolation at about 10 phr CB, which is the percolation threshold V _f ^* shown in FIG. 2a. In addition, the fact that the 10 phr CB concentration is not the percolation threshold V _f ^* of the Ny6 / CB / organoclay (5 vol%) composition increases Ny6 / CB when the organoclay addition is increased from 3 vol% to 5 vol%. / It can be seen that the dispersion state of CB in the organoclay (5% by volume) composition is not a percolation structure.

As a further basis for the content described in the above paragraph, SEM images of Ny6 / CB-based compositions with different organoclay addition rates at 20 phr CB concentration are shown in FIG. Since the 20 phr CB concentration is approximately the percolation threshold V _f ^* of the Ny6 / CB composition with 5% by volume of organoclay added, in FIG. 4b a developed “fishing net” morphology with a co-continuous CB network structure is observed. The This is in contrast to the image of FIG. 4a, which shows a relatively dispersed CB aggregate morphology, where the Ny6 / CB composition without organoclay does not achieve the percolation threshold V _f ^* at 20 phr CB concentration. Is consistent with the fact that 2 to 4 can be assumed to be caused by a high percolation phenomenon induced by the addition of organoclay. The definitions of the morphology mechanism and advanced percolation are described below.

Image analysis was performed on all SEM images to reveal additional morphological features of FIGS. FIG. 5 shows a histogram of the distribution of nearest neighbor lengths for Ny6 / CB 10 phr CB composition and Ny6 / CB 20 phr CB composition with different organoclay addition rates. CB dispersion is the distribution of CB aggregates and CB / CB (aggregate) distance within the polymer matrix. As shown in FIG. 5, the Ny6 / CB / organoclay (3% by volume) composition (FIG. 5a) and the Ny6 / CB / organoclay (5% by volume) composition (FIG. 5b) have a sharp peak in the histogram at 200 nm. Appears. These histogram peaks are the basis for the percolate structure, and 200 nm is the distance indicating the closest length for the CB / CB interaction to achieve percolation in the Ny6 polymer network. This observation supports the conclusion drawn from FIG. 2, and the 10 phr CB concentration and the 20 phr CB concentration are the percolation thresholds V _f ^* and Ny 6 for the Ny6 / CB / organoclay (3 vol%) composition, respectively. The percolation threshold V _f ^* of the / CB / organoclay (5% by volume) composition predicts the conclusion drawn from FIG.

  Further insight into the morphological features comes from the quantitative image analysis of the CB dispersion state using the Morishita quadrate method and the dispersion index of the Morishita, where the Morishita least squares and the dispersion index of the Morishita are: Morishita, M. In Memories of the Facility of Science Ser. E, Biology; Kyushu University: Fukuoka Prefecture, 1959; 2,215. Karasek, L .; Sumita, M .; Mater Sci. 1996,31,281. These references are hereby incorporated by reference into the present disclosure.

According to the Morishita method, the total area of each SEM image is divided into small equal area basic regions and the number of points in each region is calculated. The CB primary aggregate is defined as a single dot in the enlarged SEM image shown in FIG. 5, and the CB primary aggregate is a Morishita dispersion index as a function of the quadrature number q expressed by the following equation: The variation of CB dispersion with respect to I _δ is used for pattern variation.

Wherein, q is an element number obtained by equally dividing the total area of the SEM image, n _i is the number of CB primary aggregates are considered as one dot in the i-th part of the sem image, N is the, The total number of CB primary aggregates considered as dots.

Based on Equations 1-3, image analysis was performed using proprietary program software (Image Analysis for Windows, version 4.10, ASAI (copyright)). FIG. 6 is a schematic diagram showing the relationship between the dispersion index I _δ of Morishita and the number of divisions q in various dispersion modes of the CB primary aggregate.

FIG. 7 shows the dispersion index I _δ and the division number q of Morishita in Ny6 / CB composition having 10 phr CB concentration and Ny6 / CB composition having 20 phr CB concentration with different organoclay addition rates obtained from SEM images. The relationship is shown. The following observations are the basis of FIGS.

When the addition rate of organoclay is increased in a Ny6 / CB composition having a 10 phr CB concentration, the dispersion index I _{δ of} Morishita is I _δ = 1 (0 vol% organic clay added), I _δ > 1 (3 vol% organic Clay), and I _δ <1 (5% by volume organic clay added), and these change in dispersion mode fluctuations indicated by reference numerals (b), (f), and (a) in FIG. It corresponds. The above observations suggest that the distribution of CB aggregates exhibits a Poisson mode, which is an under-scattered CB aggregate morphology, when the addition rate of organoclay is 0% by volume. As the organoclay addition rate increases to 3% by volume, the dispersion transitions to a cohesive mode in which small aggregates are dispersed in Poisson mode as a whole. When the addition rate of the organic clay is 5% by volume, the dispersion becomes a regular mode.

In the Ny6 / CB composition having a 20 phr CB concentration, the dispersion index I _{δ of} Morishita varies as I _δ <1 (0 vol% organic clay added), I _δ > 1 (5 vol% organic clay added). These correspond to the dispersion mode fluctuations indicated by reference numerals (a) and (c) in FIG. This observation suggests that the presence of organoclay increases the dispersion of CB aggregates from regular mode to aggregate mode where large aggregates are dispersed in regular mode as a whole. Therefore, the CB dispersion in the Ny6 network forms a percolate network structure due to the presence of the organic clay at a low organoclay addition rate, and the CB dispersion has stability and regularity at a high organoclay addition rate. The novel electrical percolation behavior in the Ny6 / CB composition is believed to be caused by a high percolation phenomenon induced by the addition of organoclay.

  To help explain the present invention, the type of organoclay addition structure of various melt blend Ny6 compositions was determined. FIGS. 8a and 8b and FIGS. 9a and 9b show the X-ray diffraction pattern and bright-field TEM image of the Ny6 nanocomposite, the black layer shows the primary organoclay platelet and the gray / white region shows the Ny6 matrix. (All enlarged images). The X-ray diffraction pattern does not show a recognizable intensity peak, which seems to indicate that the organoclay is fully exfoliated and dispersed, as shown in the TEM image.

  As a further basis for the above observations, FIGS. 8c and 8d show X-ray diffraction patterns of Ny6 / CB compositions having 20 phr CB concentrations with different organoclay addition rates. Despite a significant amount of CB in the Ny6 nanocomposite, the X-ray diffraction pattern is a smooth curve (fully exfoliated structure), suggesting extensive layer separation due to physical separation such as delamination . However, in FIG. 9a, a recognizable intensity peak is observed, and as is evident from the TEM image, the natural clay dispersed in nylon 6-CB 20 phr has no delamination. This observation suggests that the high percolation driving force in the Ny6 / CB composition is associated with a dispersion state of the organoclay that has been at least partially or completely exfoliated.

(Morphology of hard organic carbon and brittle clay minerals)
To find evidence to support or reject the above view, high-resolution observation of real-time morphologically selected regions by STEM (× 135, Ny6 nanocomposites and Ny6 / CB compositions with different organoclay loadings 000). Its purpose is to explore the morphological evidence that can explain the mechanism of the above-mentioned advanced percolation phenomenon, in particular to explore the relationship between hard spherical CB and brittle clay platelets. 10a and 10b show bright field TEM images of various Ny6 / CB compositions with organoclay addition rates different from 20 phr CB concentration, the black spherical regions show CB primary aggregates and the gray / white regions show Ny6 The matrix is shown. The left image is an original image, and the right image is an enlarged image of a single divided TEM image. Arrows indicate primary organoclay platelets (or black monolayers). Two obvious morphological features were observed.

  CB / organoclays behave as one “nano unit” in the Ny6 matrix and negotiate between the two different elastic properties of nanoparticles (hard spherical CB and brittle clay platelets) regardless of the different organoclay loadings. (Communion), geometry, and structure are possible. This interesting “nanounit” morphology suggests that there is a strong favorable intermolecular interaction between organoclay / nylon 6 / CB under shearless viscous flow.

  As shown in FIG. 9, the brittle primary organoclay platelets are substantially deformed and partially encapsulate hard rock-like CB primary aggregates according to their geometry. The observed morphology indicates that the deformed brittle organoclay platelets have a certain tolerance for bending and / or deformation flexibility. However, it is not necessary to make direct contact with CB, and it is sufficient that they are close in the range of 1.07 to 1.42 nm separated by the interphase thickness of the Ny6 organic modifier. The thickness of the primary organoclay platelet is 0.7 nm and the length of the platelet is in the range of 200-300 nm. The diameter of primary CB particles is about 60 nm. These values are very close to the reported values (the thickness and length of the primary clay platelets are 1.0 nm and 200 nm, respectively, and the diameter of the primary CB particle morphology is 62 nm).

  Rheological measurements were used on various Ny6-based isotropic shaped disks to investigate the effects of various thermal histories on the “nano-unit” morphology of CB / organoclay behavior and shear viscous flow in the shear field. Isothermal shearing was applied. The raw materials were mixed non-isothermally using a twin screw extruder. FIG. 11 shows a TEM image (ω = 50 rad / sec, 230 ° C., 200 seconds) of the sheared portion, FIG. 12 shows a TEM image of the extruded portion (screw speed: 200 rpm, 230 ° C.), and the black spherical region is CB primary aggregates are shown, the black layer shows primary organoclay platelets, and the gray / white area shows Ny6 matrix (all enlarged images). The shear direction is indicated by an arrow. The organoclay dispersion of sheared and extruded Ny6 nanocomposites with 5 vol% organoclay loading (FIGS. 10c and 11b) is the Nylon 6 nanocomposite organoclay dispersion with irregular orientation shown in FIG. 9a. Are different, indicating the orientation of nanoscale organoclays along the shear direction. The oriented primary organoclay platelets show a further enhanced linear arrangement along the shear direction, which is an artificial reorientation of the initial clay platelets caused by mechanical shearing. The presence of the CB network in the Ny6 nanocomposite appears to have caused orientation under shear flow. However, the orientation of the organoclay dispersion is irregular. Although there are orientational irregularities caused by the presence of CB, primary organoclay platelets continue to be oriented within the CB free flow path (FIGS. 11b and 12a). An important point included in FIG. 10a is that the brittle primary organoclay platelets are substantially deformed and, according to their geometry, partially encapsulate the hard CB primary aggregates, and the CB / organoclay behavior in the shear field also A specific “nano-unit” morphology is obtained. This observation supports the observation made from FIG. 9 and this morphological data shows that the organoclay / Ny6 / CB has a favorable intermolecular interaction with novel characteristics regarding the flexibility of the primary clay platelets. Reflects the strength of interfacial bonding.

  FIG. 13 shows the mechanism we consider to be highly percolated for the thermodynamic physical / chemical intermolecular interaction between organoclay / Ny6 / CB. In the absence of organoclay, the CB dispersion state is random dispersion and cannot be controlled. By adding 3% by volume of organoclay, CB forms a conductive network and an initial percolation lower than the percolation threshold of the original Ny6 / CB system is obtained. Increasing the addition rate of organoclay further brings “stability” and / or regular dispersion into the CB dispersion, which can control the conductivity.

  Although revealing the form of interaction in a multiphase polymer material proved to be very difficult if not impossible, the organoclay / Ny6 / CB components are highly reactive. The form of interaction is due to the combination of weak physical interaction (dipole interaction) and strong chemical interaction (hydrogen bonding).

1a to 1c are schematic diagrams of different dispersion arrangements of conductive fillers in a polymer network. FIG. 2a shows the effect of different concentrations of the dispersion control agent on the conductivity of the nylon 6 / carbon black composition as a function of carbon black concentration. FIG. 2b shows the conductivity relationship of the nylon 6 / carbon black composition at different carbon black concentrations. 3a-3c are SEM images of a nylon 6 / carbon black composition having a carbon black concentration of 10 phr and containing 0% by volume, 3% by volume, and 5% by volume organoclay, respectively, FIG. FIG. 4 is a schematic diagram of an SEM image to aid in the analysis of FIGS. 4a and 4b are SEM images of nylon 6 / carbon black compositions having a carbon black concentration of 20 phr and containing 0% by volume and 5% by volume organoclay, respectively. FIG. 5a shows three histograms illustrating the distribution of closest lengths of a nylon 6 / carbon black composition having a carbon black concentration of 10 phr and containing 0%, 3%, 5% by volume of organoclay, respectively. Is shown together with an enlarged SEM image of each composition. FIG. 5b shows two histograms for each composition illustrating the distribution of closest lengths of a nylon 6 / carbon black composition having a carbon black concentration of 20 phr and containing 0 vol% and 5 vol% organoclay, respectively. Shown with enlarged SEM image of the object. FIG. 6 is a schematic diagram of the relationship between the dispersion index I _δ of Morishita and the division number q in various dispersion modes of the carbon black primary aggregate. FIG. 7 shows the relationship between the Morishita dispersion index I _δ and the number of divisions q in the nylon 6 / carbon black composition. Figures 8a and 8b show X-ray diffraction patterns of nylon 6 nanocomposites with (a) 3% by volume organoclay concentration and (b) 5% by volume organoclay concentration, respectively, with the black layer being the primary organoclay The platelets are shown, the gray / white area shows the Ny6 matrix (all magnified images), FIGS. 8c and 8d have a carbon black concentration of 20 phr, (c) an organoclay concentration of 3 vol% and ( d) Nylon 6 / carbon black X-ray diffraction pattern having an organic clay concentration of 5% by volume. Figures 9a and 9b show X-rays of a nylon 6 / carbon black composition having a carbon black concentration of 20 phr and (a) 3 vol% natural clay concentration and (b) 3 vol% organic clay concentration, respectively. A diffraction pattern and an enlarged TEM image are shown. FIG. 10a shows a TEM image of a nylon 6 / carbon black composition having a carbon black concentration of 20 phr and having an organoclay concentration of 3% by volume, the black spherical regions showing carbon black primary aggregates, gray / white Region indicates nylon 6 network. FIG. 10b shows a TEM image of a nylon 6 / carbon black composition having a carbon black concentration of 20 phr and an organoclay concentration of 5% by volume, the black spherical areas showing the carbon black primary aggregates, gray / white The area shows a nylon 6 network. FIG. 11a is a TEM image of a sheared nylon 6 / carbon black composition having a carbon black concentration of 20 phr and containing 5 vol% organoclay. FIG. 11b is a TEM image of a sheared nylon 6 / carbon black composition having a carbon black concentration of 20 phr and containing 5 vol% organoclay. FIG. 11c is a TEM image of a sheared nylon 6 composition containing no carbon black and containing 5 vol% organoclay. FIG. 12a shows an enlarged TEM image of an extruded nylon 6 / carbon black composition (screw speed: 200 rpm, 230 ° C.) having a carbon black concentration of 20 phr and an organoclay concentration of 5% by volume, where the black spherical regions are Carbon black primary aggregates are shown, the black layer shows primary organoclay platelets, and the gray / white region shows nylon 6 network. FIG. 12b shows an enlarged TEM image of an extruded nylon 6 / carbon black composition (screw speed: 200 rpm, 230 ° C.) that does not contain carbon black and has an organic clay concentration of 5% by volume, with the black spherical region being the primary carbon black Aggregates are shown, the black layer shows primary organoclay platelets, and the gray / white area shows nylon 6 network. FIG. 13 is a schematic diagram of the proposed mechanism of organoclay addition-induced percolation phenomenon at the non-shear viscosity of the molten polymer.

Claims (12)

A polymer composition comprising:
A polymer resin;
A conductive filler;
A dispersion control agent that promotes a substantially uniform arrangement of the conductive filler throughout the polymer composition;
Including
A polymer composition substantially free from polycyclic aromatic compounds. In claim 1,
A polymer composition, wherein the polymer network comprises a thermoplastic polymer. In claim 1,
A polymer composition, wherein the polymer network comprises a thermosetting polymer. In claim 1,
A polymer composition, wherein the polymer network comprises a polymer selected from the group consisting of polyamides, polyesters, and polyolefins. In claim 1,
A polymer composition, wherein the conductive filler is selected from the group consisting of carbon black, conductive carbon black, and carbon nanotubes. A polymer composition comprising:
A polymer resin;
A conductive filler;
An amount of non-conductive filler effective to increase the conductivity of the polymer composition as compared to the same composition without sub-micron to nano-sized particles;
Including
A polymer composition substantially free from polycyclic aromatic compounds. In claim 6,
A polymer composition, wherein the conductive filler is selected from the group consisting of carbon black, conductive carbon black, and carbon nanotubes. In claim 6,
A polymer composition, wherein the non-conductive filler is a particulate filler having a submicron or nanometer particle size. In claim 6,
A polymer composition having a percolation threshold lower than the percolation threshold of the same polymer composition without the non-conductive filler. A polymer composition comprising:
A polymer resin;
A conductive filler;
An amount of sub-micron to nano-sized non-conductive filler effective to reduce the percolation threshold of the polymer composition as compared to the percolation threshold of the same composition without sub-micron to nano-sized particles;
Including
A polymer composition substantially free from polycyclic aromatic compounds. A polymer composition comprising:
A polymer resin;
A conductive filler;
An amount of a dispersion control agent effective to minimize the sensitivity of the conductivity of the polymer composition to changes in the concentration of the conductive filler in a desired conductivity region;
Including
A polymer composition substantially free from polycyclic aromatic compounds. Identifying a desired conductivity range including the desired conductivity;
Adding an effective amount of a dispersion control agent to the polymer resin to minimize the conductivity sensitivity of the polymer composition within the desired conductivity range;
Adding a conductive filler to the polymer resin, and adjusting the polymer composition to the target conductivity;
A method for controlling the electrical conductivity of a polymer composition.